Mechanical Technology - Floating Element System: When designing a lens, Tokina calibrated its astigmatism at the points between minimum focus distance and infinity so that it will give the better image results at each settings. However, when there are large differences between the focus limits, effect calibration is not possible. A floating element system incorporates optical elements that move in proportion to the focus setting of the lens. This allows astigmatism to be corrected. Many Tokina lenses employ floating element systems to provide optimum correction of astigmatism from minimum focus distance to infinity.

Internal Focus System: The internal focusing system has a number of advantages including: faster focusing, improved handling due to fewer movements near the centre of gravity, more compact lens designs, superior use of filters because the barrel with the filter thread does not rotate.

Focus Clutch Mechanism: Tokina AT-X PRO series lenses feature the patented "Focus Clutch" Mechanism for switching the lens between auto focus and manual focus modes. The manual focusing ring can move (be snapped) back and forth between an AF and MF position. When the focusing ring is forward in the AF position, it is not engaged to any of the internal focus gearing and will turn freely. Without the added weight of the metal ring the camera can auto focus the lens more quickly and smoothly.

For manual focus, simply rotate the focus ring the way to one side or the other on the focus travel, either infinity or it's closest focusing distance, then pull back (towards the mount plate) on the manual focus ring. While pulling back, rotate the ring from one side of the focus travel to the other. When the gears align, the focus ring will snap back into the MF position and the lens can be focused manually.

To return the manual focus ring to auto focus mode, simply snap the ring forward from any point.